---
title: "What is the significance of the final keyword when applied to classes, methods, and variables?"  
description: "What is the significance of the final keyword when applied to classes, methods, and variables?"  
author: "Anubhav Sharma"  
published: 2024-07-18  
updated: 2024-07-18  
canonical: https://www.mindstick.com/forum/160946/what-is-the-significance-of-the-final-keyword-when-applied-to-classes-methods-and-variables  
category: "java"  
tags: ["java", "javac"]  
reading_time: 3 minutes  

---

# What is the significance of the final keyword when applied to classes, methods, and variables?

What is the significance of the final [keyword](https://www.mindstick.com/forum/33572/sql-inner-join-keyword) when applied to classes, [methods](https://www.mindstick.com/articles/13060/runny-nose-remedy-methods-that-work-best), and [variables](https://www.mindstick.com/articles/715/php-variables)?

## Replies

### Reply by Ravi Vishwakarma

The `final` keyword in Java can be applied to classes, methods, and variables, and it serves different purposes in each context. Here is an explanation of its significance:

#### 1. Final Classes

When a class is declared as `final`, it cannot be subclassed. This means no other class can extend a `final` class.

## Significance:

- **Security:** Prevents inheritance, which can be useful when creating immutable classes or ensuring the integrity of a class's behavior.
- **Performance:** The JVM can optimize calls to final classes more effectively because it knows that the class will not be extended.

## Example:

```java
public final class ImmutableClass {
    private final int value;

    public ImmutableClass(int value) {
        this.value = value;
    }

    public int getValue() {
        return value;
    }
}

// This will cause a compile-time error
// public class SubClass extends ImmutableClass {}
```

#### 2. Final Methods

When a method is declared as `final`, it cannot be overridden by subclasses.

## Significance:

- **Consistency:** Ensures that the method's behavior remains unchanged across all subclasses.
- **Security:** Prevents subclasses from altering crucial methods, maintaining the integrity of the class's behavior.
- **Performance:** The JVM can optimize calls to final methods more effectively.

## Example:

```java
public class ParentClass {
    public final void show() {
        System.out.println("This is a final method.");
    }
}

public class ChildClass extends ParentClass {
    // This will cause a compile-time error
    // public void show() {}
}
```

#### 3. Final Variables

When a variable is declared as `final`, its value cannot be changed once it is initialized, this applies to instance, static, and local variables.

## Significance:

- **Constants:** Useful for defining constants. A final variable acts as a constant whose value is set once and cannot be modified.
- **Immutability:** Helps create immutable objects by ensuring that the state cannot be changed after construction.
- **Thread Safety:** Reduces data corruption risks in concurrent applications by ensuring that the value remains constant after initialization.

## Example:

```java
public class Constants {
    public static final double PI = 3.14159;

    public static void main(String[] args) {
        final int fixedValue = 10;

        // This will cause a compile-time error
        // fixedValue = 20;
    }
}
```

the `final` keyword appropriately, developers can **create more secure, reliable, and optimized Java applications.**


---

Original Source: https://www.mindstick.com/forum/160946/what-is-the-significance-of-the-final-keyword-when-applied-to-classes-methods-and-variables

Copyright © MindStick Software Pvt. Ltd. This Markdown version is provided for developers, AI systems, and offline reading.